Programmable sample rate analog to digital converter and method for use therewith

Abstract

A programmable sample rate ADC includes a delta sigma modulator for producing a digital signal, and a programmable decimation filter, that includes X stages of integration, a down-sampling stage for down-sampling by a factor of N, and Y stages of differentiation. The programmable sample rate ADC produces a digital output signal at a substantially constant frequency.

1. A radio receiver front end for receiving a received radio signal having a plurality of channel signals, each of the plurality of channel signals being modulated at one of a corresponding plurality of carrier frequencies, and for converting a selected one of the plurality of channel signals into a digital baseband signal, the radio receiver front end comprising:
 a channel selector, for producing a control signal that corresponds to a selected one of the plurality of channels; 
 a local oscillator, operatively coupled to a reference oscillation, for producing a local oscillation signal at a local oscillation frequency, the local oscillation frequency based on the control signal; 
 an analog to digital converter module, operatively coupled to a modulated signal, the modulated signal operably coupled to the received radio signal, and a variable frequency clock signal that varies as a function of the local oscillation frequency, the analog to digital converter module for producing a digital signal; and 
 a programmable decimation filter, operatively coupled to the digital signal and the control signal for producing the digital baseband signal at a substantially constant frequency. 
 
     
     
       2. The radio receiver front end of  claim 1  wherein the programmable decimation filter includes a down-sampling stage for down-sampling by a factor of N that is controlled, based on the control signal. 
     
     
       3. The radio receiver front end of  claim 1  wherein the programmable decimation filter includes X stages of integration and wherein X is at least one. 
     
     
       4. The radio receiver front end of  claim 1  wherein the programmable decimation filter includes Y stages of differentiation and wherein Y is at least one. 
     
     
       5. The radio receiver front end of  claim 4  wherein X=Y. 
     
     
       6. The radio receiver front end of  claim 1  wherein the analog to digital converter module includes a delta sigma modulator. 
     
     
       7. A method for use in a radio receiver front end for receiving a received radio signal having a plurality of channel signals, each of the plurality of channel signals being modulated at one of a corresponding plurality of carrier frequencies, and for converting a selected one of the plurality of channel signals into a digital baseband signal, the radio receiver front end comprising:
 generating a local oscillation signal at a local oscillation frequency, the local oscillation frequency based on a selected one of the plurality of channels; 
 analog to digital converting an intermediate frequency signal to a digital signal based on a variable frequency clock signal that varies as a function of the local oscillation frequency; 
 integrating the digital signal to produce an integrated signal; and 
 downsampling the integrated signal by a variable factor N, to produce a down-sampled signal having a substantially constant frequency. 
 
     
     
       8. The method of  claim 7  further comprising:
 differentiating the down-sampled signal to produce the digital output signal. 
 
     
     
       9. The method of  claim 7  wherein, the factor N is selected based on a control signal so as to provide the substantially constant output sampling frequency.